#include <iostream>
#include <math.h>
using namespace std;

double n;

int main(void)
{
    scanf("%lf", &n);
    double l, r, mid, tmp;
    if (n < 0)
    {
        l = min(n, -1.0);
        r = 0;
    }
    else
    {
        l = 0;
        r = max(n, 1.0);
    }

    while (r - l > 1e-8)
    {
        mid = (r + l) / 2;
        tmp = pow(mid, 3);
        if (tmp < n)
            l = mid;
        else if (tmp > n)
            r = mid;
        else
            break;
    }
    printf("%.6f", mid);
}